1. Field of the Invention
The present invention relates to a disk drive which includes a plurality of optical heads for performing a recording and/or reproducing operation of a data on an optical disk by light, and selects an optical head to be used depending on a condition so as to perform the recording and/or reproducing operation of the data on the optical disk corresponding to the optical head.
2. Description of the Background Art
A recording/reproducing optical disk drive in which a recording or reproducing operation is performed, by using optical beam, on a disk-shaped recording medium such as CD or DVD having further high recording density, and an optical disk medium used in the above disk drive have been widespread use. In addition, recently, technology for further high recording density has been increasingly developed.
As recording and reproducing type of the device and the medium, there are various kinds depending on its usage such as read-only type, recordable type or rewritable type. As seen in a relation between CD and DVD, the recording/reproducing forms has been widely ranged in view of a difference of a wavelength of a light source used in the recording/reproducing operation.
Thus, there are wide variety of optical disk drives and optical disk media used therein in the present circumstances, and the device and medium have to correspond to each recording and reproducing operations. Among the devices, especially an optical head which directly emits and receives optical beam is ideally constituted by one head which can correspond to the various recording and reproducing forms or recording density.
However, it is difficult for the optical head to have characteristics required for each of the combinations of a plurality of wavelengths and various kinds of optical systems in many cases. As a result, sufficient performance margin cannot be provided and its characteristics are varied because of a subtle working condition and then it becomes unusable in some cases. In order to avoid the above-mentioned problems, it is preferable in many cases that a plurality of optical heads which specialize wavelength of the optical beam or the optical system are used and a recording or reproducing operation is performed on a disk corresponding to a specific optical head in view of a size of the optical head, reliability margin, manufacturing and adjustment cost, or cost of parts. In other words, it is preferable that each optical head corresponding to a standard of the recording/reproducing system to be used is mounted on the device as it is.
From this point of view, a constitution of a disk drive on which a plurality of optical heads corresponding to respective standards are mounted is disclosed in Japanese Patent No. 2943918, for example.
FIG. 24 is a perspective view showing the conventional optical disk.
A description is made of a schematic constitution of this example. According to this example, there is provided an optical disk drive which comprises two optical heads and performs a recording or reproducing operation on an optical disk corresponding to each of the optical heads.
Reference numerals 501a and 501b designate a first optical head and a second optical head each corresponding to the optical disk on which the recording or reproducing operation can be performed in the optical disk drive in this example, reference numerals 502aL and 502aR designate first small guide shafts for supporting the first optical head 501a when housed, and reference numerals 502bL and 502bR designate second small guide shafts for supporting the second optical head 501b when housed. The first small guide shafts 502aL and 502aR and the second small guide shafts 502bL and 502bR constitute an optical head housing part 551 together with a rotating plate 503 and a support base 504. The rotating plate 503 is supported by the support base 504 so as to be rotated around a turn spindle 503A by rotating means (not shown) in the direction of an arrow 801. In addition, the first small guide shafts 502aL and 502aR and the second small guide shafts 502bL and 502bR are provided so as to be parallel to each other and perpendicular to the rotating plate 503. A distance between a plane surface containing the first small guide shafts 502aL and 502aR and the turn spindle 503A is equal to a distance between a plan surface containing the second small guide shafts 502bL and 502bR and the turn spindle 503A.
Reference numeral 505 designates an optical disk on which the recording or reproducing operation is performed in the device, reference numeral 506 designates a disk motor for rotating the optical disk 505, reference numerals 507L and 507R designate guide shafts for guiding the first optical head 501a or the second optical head 501b in one radius direction of the optical disk 505 when the recording or reproducing operation is performed on the optical disk 505, and reference numeral 508 designates a transport support which integrally supports the disk motor 506, and the guide shafts 507L and 507R. In addition, the support base 504 and the transport support 508 are supported by a base board 509.
The optical heads 501a and 501b are transported by transport driving means (not shown) over the guide shafts 507L and 507R so that it can scan the optical disk 505 in one radius direction to perform the recording or the reading operation.
A function or an operation of each component is described hereinafter.
The first optical head 501a and the second optical head 501b are housed in the optical head housing part 551 while supported by the first small guide shafts 502aL and 502aR, and the second small guide shafts 502bL and 502bR, respectively. At this time, objective lenses 501aA and 501bA of the optical heads 501a and 501b, respectively are opposed to each other in the optical head housing part 551.
Referring to FIG. 24, the small guide shaft 502aL and the guide shaft 507L, and the small guide shaft 502aR and the guide shaft 507R are linearly arranged, respectively. The first optical head 501a is moved from the housing part 551 to the side of the transport support 508 in the direction of an arrow 802 and the first optical head 501a can be transported on the guide shafts 507L and 507R so as to perform the recording or reproducing operation on the optical disk 505 by using the first optical head 501a. 
In addition, when the rotating plate 503 is rotated by the rotation driving means (not shown) in either direction of the directions of arrows 801, by 180 degrees, the small guide shaft 502bR and the guide shaft 507L, and the small guide shaft 502bL and the guide shaft 507R are linearly arranged, respectively. Then, the second optical head 501b is moved from the housing part 551 to the side of the transport support 508 in the direction of the arrow 802, so that the second optical head 501b can be transported on the guide shafts 507L and 507R so as to perform the recording or reproducing operation on the optical disk 505 by using the second optical head 501b. 
When each optical head completes the recording or the reproducing operation, or when the optical head is to be exchanged with the other optical head after the optical head is moved to the side of the transport support 508, for example, because it is determined that the optical head cannot perform the recording or reproducing operation as a result of detection of the kind of the optical head set on the disk motor 506 by the optical head on the side of the transport support 508, the above process is reversely performed, that is, the optical head is moved from the transport support 508 to the housing part 551 and the other optical head is moved from the housing part 551 to the transport support 508 again.
According to the above device, when the recording or reproducing operation is performed on the specific optical disk 505, for example, either one of the first optical head 501a or the second optical head 501b is selected and moved to the side of the transport support 508. Prior to this operation, it is necessary to distinguish the kind of the optical disk 505 in order to determine which one of the first optical head 501a and the second optical head 501b is appropriate to be used.
However, in the above-mentioned prior art, the disk corresponding to both the first optical head 501a and the second optical head 501b, is a type of disk which does not use a containing case or the like, that is, a so-called bare disk. Therefore, it is necessary to determine that the optical head is appropriate to the disk or not by mounting one optical head to the transport support 508, performing the recording or reproducing operation and reading a focus signal or a tracking signal, for example. At this time, although the recording and/or reproducing operation can be continued when the mounted optical head is appropriate, the optical head has to be exchanged with the other one when it is not appropriate. In this case, time for starting the recording or reproducing operation is delayed for that. Thus, when a user wants to record data, its timing could be lost. It is to be noted that the wording of “recording and/or reproducing” means “at least one of recording and reproducing” in the specification.